Why were the WHO and CDC reluctant to recommend masks for the general public?

For several weeks, health professionals, political leaders and even the World Health Organization have told the public that people do not need to use protective face masks unless they are sick or caring for someone with COVID-19.

Experts agree that medical-grade protective gear, such as N95 respirators, should be reserved for health workers, but officials from the Centers for Disease Control and Prevention in the US said on Monday (30th March) they were reviewing their recommendations after new data showed nearly a quarter of those infected did not show symptoms, meaning they were infectious perhaps without realizing it.